Magnetic disk drives are becoming increasingly smaller in order to meet the portability requirements of notebook computers. Consequently, space is at a premium in all dimensions. As a result, there is a limited volume in which to employ a coil for a voice coil motor (VCM) for actuating a head-arm assembly.
Generally, rotary head actuators are used in the small disk drives associated with notebook computers. Head-arm assemblies are pivotally mounted about a fixed pivot shaft. One end of the arm carries the read/write head, and the other end of the arm is disposed in and forms part of a VCM. The VCM provides the pivotal motion of the head-arm assembly.
Moving a head-arm assembly from a first position to a second position with respect to a platter (disk) surface is a necessary feature of a disk drive. Providing an ability to move the head-arm assembly quickly and accurately (including mechanical stability) with low power consumption is a desirable goal. Having the ability to accurately position the head-arm assembly results in an increase in the number of tracks per inch (TPI) which may be employed.
Moreover, notebook computers are often used in mobile environments. Thus, displacement of a head-arm assembly owing to side loading must be severely restricted. Consequently, head-arm assemblies are made stiffer; in other words, more torque is required to pivotally move the head-arm assembly.
Therefore, it is desirable to provide a head-arm and VCM assembly which has increased torque over comparable prior art assemblies for the small volume available.